Die Charakterisierung von Nanopartikeln erfordert eine Messung des Dispersitätszustandes bei allen Schritten der Herstellung - von der Synthese bis zum fertigen Produkt. Dafür ist eine leistungsfähige Partikelmesstechnik notwendig, deren Methoden bei der Beschreibung des komplexen Materialverhaltens helfen können. Die Ultraschalldämpfungsspektroskopie ist eine Messmethode, die zur prozessbegleitenden Charakterisierung hochdisperser Pulver und Suspensionen geeignet ist. Mit Vergleichen von Messungen und Modellrechungen wurde festgestellt, dass für die Ultraschalldämpfungs-Modellierung in Dispersionen homogener Partikel ein auf dem Phänomen der elastischen Streuung basierendes Modell praktisch relevant ist. Dies betrifft sowohl die Anwendung zur Messung in Suspensionen als auch in Emulsionen homogener Partikel. Bei einem Vergleich von Modellrechungen und Messungen für ein System poröser Partikel bzw. Aggregate wurde das Modell der Streuung an poroelastischen Kugeln als geeignet zur Beschreibung der Dämpfung disperser Systeme identifiziert. Bei Vorhandensein grober Partikel in Suspensionen nanoskaliger Systeme ist somit eine korrekte Auswertung der Partikelgröße möglich; der bislang übliche Messbereich wurde erweitert. Sekundärer Schwerpunkt der Arbeit ist die Diskussion der numerischen Modellanwendung. Es werden weiterhin Lösungsmöglichkeiten zur Dämpfungsberechnung und zur Berechnung der Größenverteilungen beschrieben. Des Weiteren wurden Anregungen für Entwickler von Ultraschallspektrometern abgeleitet.

<p>Poznavanje spektra x-zračenja kao i drugih osobina je od izuzetnog&nbsp; značaja&nbsp; kako za planiranje radijacione terapije tako i sa aspekta za&scaron;tite pacijenta i osoblja. Takođe, poznavanje svojstava&nbsp; neutrona&nbsp; nastalih&nbsp; u interakciji fotona sa materijalima<br />oko akceleratora, je od izuzetnog značaja sa dozimetrijskog aspekta. Poslednjih godina sve se vi&scaron;e upotrebljavaju linearni akceleratori bez homogenizacionog filtera tzv. FFF (<em>Flatteninig Filter Free</em>), a kako su karakteristike snopa u toma načinu rada akceleratora jo&scaron; uvek nedovoljno ispitane, njima smo posvetili posebnu pažnju. Urađena su i detaljna dozimetrijska merenja fotona kako u radu sa homogenizacionim filterom (FF) tako i bez njega (FFF), kao i dozimetrijsko merenje neutrona. Direktno merenje samog<br />spektra nekim od detektora (NaI ili HPGe) nije moguće zbog visokih intenziteta stoga smo u radu koristili indirektne metode i to aktivacionu analizu i atenuacionu analizu.<br />Urađena su detaljna dozimetrijska merenja ekvivalentne doze neutrona u terapijskoj sobi sa dva zaokreta hodnika i na osnovu rezultata predložena je korekcija metode za izračunavanje neutronske doze na ulaznim vratima.&nbsp; Fotoaktivacionimmerenjima, gde su se u oba načina rada terapijskog&nbsp; akceleratora pratile aktivnosti izomera ^115m In, ustanovljeno je da se kod dva tipa&nbsp; akceleratora&nbsp; (Elekta Versa HD, Varian TrueBeam)&nbsp; oblik spektra u visokoenergetskom delu znatno razlikuje, kao i da postoji razlika u obliku spektra na ivici polja i u njegovoj sredini.&nbsp; Atenuacionom analizom&nbsp; na osnovu&nbsp; standardnog metoda rekonstrukcije fotonskog spektra putem Laplasovih transforma, dobijene su izvesne razlike u oblicima spektara za dva režima rada. Takođe,&nbsp; rekonstrukcijom spektra putem odabira parametara korekcine funkcije koja bi teorijski oblik spektra (&Scaron;ifova funkcija) trebao da prevede u realan spektar za oba režima rada dobijene su izvesne razlike u oblicima spektra. Dozimetrijska merenja fotonske doze na ulaznim vratima terapijske sobe sa&nbsp; jednim zaokretom, sa i bez homogenizacionog filtera za različite veličine polja i sa i bez vodenog kanistera koji simulira pacijenta u snopu, pokazuju da je izmerena&nbsp; doza na ulaznim vratima u FFF modu rada uvek niža od izmerene doze u slučaju da se koristi homogenizacioni filter.</p> / <p>Knoweledge of the x-ray spectrum as well as other characteristics of the beam is of&nbsp; great&nbsp; importance both for the planning of radiotherapy as well as for the protection of patients and staff. Also, the knowledge of the neutron properties generated&nbsp; in the interaction of photons with materials around the accelerator is of great importance from the dosimetric aspect. In recent years, linear accelerators are increasingly used without a flattening filter, so-called FFF (<em>Flatteninig Filter Free</em>), and as the characteristics of the&nbsp; beam in this mode of operation of the accelerator&nbsp; are still insufficiently&nbsp; investigated, we paid special attention to them. Detailed dosimetric measurements of photons were performed both with (FFF) and without the flattening&nbsp; filter (FF), as well as the dosimetric measurement of the neutron. Direct&nbsp; measurement of the spectrum itself by detectors (NaI or HPGe) is not possible due to&nbsp; high intensities, therefore, we used indirect methods in this work, both activation analysis and attenuation analysis. Detailed&nbsp; dosimetric measurements of the&nbsp; neutron&nbsp; equivalent dose in the therapeutic&nbsp; room with two band maze&nbsp; were made and based on the results, correction of the method for calculating the neutron dose at the entrance door was proposed. It was found by photoactivation measurements, where the activities of the isomer ^115mIn were investigated, that in the two types of accelerators (Elekta Versa HD, Varian TrueBeam) the spectrum shape in the high-energy part is significantly&nbsp; different, and that there is a spectrum difference in the edge of the field and in the middle of the field. Attenuation analysis, based on the standard method of reconstructing the photon spectrum through Laplace transforms, showed&nbsp; some differences in the spectra of&nbsp; the two working&nbsp; modes&nbsp; of accelerators. Also, by reconstructing the spectrum by correction function&nbsp; that&nbsp; should transform&nbsp; the&nbsp; theoretical spectrum&nbsp; form (the Schiff function)&nbsp; into a real spectrum for both modes of operation, certain differences&nbsp; in spectrum shapes were&nbsp; obtained. Dosimetric measurements of the photon dose at the entrance door of treatment room&nbsp; with a single maze with and without a homogenizing filter for different field sizes and with and without a water canister&nbsp; which simulates&nbsp; the patient in a beam showed&nbsp; that the measured dose at the entrance door in the FFF mode is always lower&nbsp; than the measured doses in FF mode.</p>

Orientador: Maria Solange Gurgel de Castro Fontes / Resumo: As fachadas verdes são variedades de jardins verticais em que a vegetação do tipo trepadeira cresce e se desenvolve em superfícies verticais e podem ser classificadas em diretas e indiretas. A primeira cresce diretamente na parede da edificação, enquanto a segunda necessita de estruturas de suporte fixadas ou afastadas da mesma. Devido ao poder de sombreamento e às funções biológicas das trepadeiras, as fachadas verdes funcionam como dispositivos de amenização térmica, uma vez que sua cobertura vegetal bloqueia a passagem de grande parte da radiação solar para dentro da edificação. Neste contexto, esta pesquisa, de caráter experimental, teve como objetivo determinar e quantificar a atenuação de radiação solar de fachadas verdes indiretas com três diferentes espécies de trepadeiras (Ipomoea horsfalliae, Passiflora Edulis e Thunbergia grandiflora) em um espaço de transição situado no Campus da Universidade Estadual Paulista, em Bauru-SP. A pesquisa objetivou, ainda, verificar a influência das fachadas verdes nos microclimas (temperatura do ar, de globo e umidade absoluta do ar) de um espaço de transição com e sem a influência das mesmas. Além disso, foram analisados os aspectos morfológicos das espécies selecionadas que estão diretamente ligados com seu Potencial de Sombreamento (PSO) e, consequentemente, a atenuação da radiação solar promovida pela vegetação. Os resultados demonstram que, quanto maior o PSO das espécies, maior seu poder de atenuação da radiação solar. Assim, f... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The green facades are varieties of vertical gardens in which the climber grows and develops on vertical surfaces and can be classified as direct and indirect. The first one grows directly on the wall of the building, while the second needs support structures attached to or away from it. Due of their shading power and the biological functions of climbers, green facades act as thermal mitigation devices, since their vegetation cover blocks the passage of much of the solar radiation into the building. In this context, this experimental research aimed to determinate and quantify the solar radiation attenuation of indirect green facades with three different species of climbers (Ipomoea horsfalliae, Passiflora edulis e Thunbergia grandiflora) in a transitional space located on the Campus of the State University of São Paulo, in Bauru-SP. The research also aimed to verify influence of green facades on local microclimates (air temperature, globe temperature and absolute air humidity) at points with influence of green facades and without influence of them. In addition, the morphological aspects of the selected species that are directly linked with their Shading Potential (PSO) and, consequently, the solar radiation attenuation promoted by the vegetation were analyzed. The results show that the higher the PSO of the species, the greater their solar radiation attenuation power. Thus, maximum attenuations of up to 92, 94 and 90% were obtained for Passiflora edulis (PSO 0,75), Ipomoea hor... (Complete abstract click electronic access below) / Mestre

Magister Scientiae (Integrated Water Resource Management) / River catchments in agricultural areas are strongly influenced by runoff from cultivated or grazed fields, and nutrient loading of these fields can result in large quantities of nitrates and phosphates being transported to rivers in surface runoff. In intensively farmed areas, nutrient loading is often so high that large quantities of nitrates and phosphates are transported to streams in surface runoff. Within these areas, strips of natural riparian vegetation and wetlands are critical in providing nutrient uptake functions that can reduce the load entering streams. A wetland can be a source, sink or transformer of nutrients, where fine sediments such as silt and clay have the ability to store and trap considerable amounts of phosphorus through adsorption and precipitation processes. Therefore, the determination of phosphorus adsorbed to fine sediment is important in understanding the role and value of wetlands in agricultural landscapes, and is the main focus of this study. The aim of the study is to evaluate an indicator-based approach, WET-EcoServices, to assess wetland sediment and phosphate trapping, through comparison with field survey data. The study focuses on spatial analysis and field survey of three Hydrogeomorphological (HGM) units classified for the Wiesdrift wetland on the Nuwejaars River, Cape Agulhas. The three HGM units are classified as: a floodplain wetland at the inlet of the system, a channelled valley-bottom wetland towards the middle part of the system and a floodplain wetland towards the outlet of the system. In-field observations were recorded for hydrogeomorphic and vegetation characteristics for each HGM Unit. AstroTurf mat sediment samples, grabbed channel bed and floodplain sediment samples were analysed for particle size and orthophosphate concentrations, while suspended sediment masses were recorded from three pairs of time-integrated sediment samplers located near the inlet, near the middle, and near the outlet of the wetland. Statistical analysis showed that orthophosphate concentrations are associated with fine sediment. Thus, the orthophosphate concentrations follow the distribution of silt on the Wiesdrift wetland. The dominant vegetation along transect 2, at which the highest concentrations of orthophosphate was found, is occupied by Typha capensis and Cyperus textilis. The percentage of fine sediment (silt) ranged between 0-37%, where the remaining percentage was sand. There was also a significant positive correlation between orthophosphate concentration and silt (Spearman’s rank-order correlation: rs = 0.692, N = 70, P < .001). The largest total sediment amount was found at Outlet 1 and Outlet 2 in the HGM unit 3 of the Wiesdrift wetland, with a value of 0.653 g. Overall, orthophosphate concentrations ranged between 0 mg/kg and 31320 mg/kg within the Wiesdrift wetland. WET-EcoServices determines an average score for phosphate trapping from on-site indicators such as hydrological zones, vegetation structure and soil texture/permeability. The dispersal of fine sediment and associated adsorbed phosphate is more complex than can be determined by a tool like WET-EcoServices because the tool captures the long-term mean conditions of a wetland system that determines the overall uptake of phosphates over extended time periods, thus future wetland assessments is recommended to take place over a longer period than this study. However, the field results of orthophosphate distribution are generally consistent with the findings from WET-EcoServices, further motivating for the use of the tool in wetland management applications.

No description available.

The use of ultrasound contrast agents increases the information available for reconstruction during ultrasound imaging. Previously studied microbubbles, consisting of a gas core, are subject to limitations such as a short lifetime and a large size. Droplets with a liquid perfluorocarbon core that is stabilized by cellulose nanofibers eliminate these drawbacks, but require further investigation. By studying the frequency-dependent attenuation profile of the cellulose nanofiber coated perfluorocarbon droplets within an ultrasound field, information about the droplets as oscillators can be retrieved, enabling characterization of their physical properties. In this study, the frequency-dependent attenuation profile was experimentally acquired and compared between two concentrations, using flat transducers covering the frequency range of 1-15 MHz. The data collected in the time domain was processed and transformed into the frequency domain and the attenuation was calculated across the entire frequency range. Among the frequencies studied, the attenuation increases with frequency and covers the range of approximately 0.25-8.3 dB/cm and 0.01-3.3 dB/cm at the concentrations of 50 million droplets/ml and 10 million droplets/ml respectively. The attenuation reaches a minimum at 3 MHz within the highest concentration, compared to 4.43 MHz within the lowest. The increase of the attenuation with frequency is explained by the droplets not exhibiting large oscillations within the range covered. It is probable that the droplets do exhibit oscillations, due to a viscosity lower than that of water, but a resonance frequency is not found within the spectrum studied. This could be explained by a shell elasticity or a small droplet radius placing the resonance frequency outside of the spectrum studied, or high levels of damping broadening the resonance peak. Localizing the resonance frequency would enable characterization of these physical properties of the cellulose nanofiber shell as well as the perfluorocarbon liquid core of the droplets. The increase of the attenuation with frequency demonstrates that the droplets do not produce a maximized amount of scattering at a specific frequency within the range studied, which is observed among other oscillating particles implemented as ultrasound contrast agents. The attenuation is, however, larger than that of blood across all frequencies except for those among which the attenuation reaches its minimum. Potential errors that are affecting the results include droplet vaporization, the formation of flocs after the mechanical agitation has ceased, the experimental setup, the settings on the pulse generator, the sensitivity of the transducers and the processing code.

[pt] Este trabalho examina o problema da atenuação por chuvas na propagação da energia em freqüências superiores a 10 ghz, com especial ênfase na aplicação dos resultados em regiões de clima tropical. São discutidos em detalhes os métodos existentes para caracterizar a distribuição estatística pontual da precipitação em uma região. Apresenta-se uma solução semi-empírica para a questão da não uniformidade espacial da distribuição de chuvas em um percurso, empregando o conceito de precipitação equivalente e dados de inúmeros trabalhos experimentais publicados na literatura técnica para diversas freqüências e distancias. Finalizando é feito um exemplo ilustrativo do método proposto, tomando por base os dados pluviográficos do Rio de Janeiro. / [en] This work deals with the problem of rainfall attenuation at frequencies above 10 GHz. Particular enphasis is given to the application of the final results for communications links in a tropical region. The proposed nethods to characterize the punctual rainfall statistical distribution in a specific region are discussed in detail. A solution to the problem of a non-uniform spatial distribution of the rainfall through the propagation path is presented, the concept of equivalent precipitation being applied. A big amount of experimental data from the technical literature was utilized, for different frequencies and distances. Finaly, an example of the proposed method is presented, along with an application based upon Rio de Janeiro rain data.

Yes / This paper investigates the stabilisation problem and consider transient optimisation for a class of the multi-input-multi-output (MIMO) semi-linear stochastic systems. A control algorithm is presented via an m-block backstepping controller design where the closed-loop system has been stabilized in a probabilistic sense and the transient performance is optimisable by optimised by searching the design parameters under the given criterion. In particular, the transient randomness and the probabilistic decoupling will be investigated as case studies. Note that the presented control algorithm can be potentially extended as a framework based on the various performance criteria. To evaluate the effectiveness of this proposed control framework, a numerical example is given with simulation results. In summary, the key contributions of this paper are stated as follows: 1) one block backstepping-based output feedback control design is developed to stabilize the dynamic MIMO semi-linear stochastic systems using a linear estimator; 2) the randomness and probabilistic couplings of the system outputs have been minimized based on the optimisation of the design parameters of the controller; 3) a control framework with transient performance enhancement of multi-variable semi-linear stochastic systems has been discussed. / Higher Education Innovation Fund (No. HEIF 2018-2020), De Montfort University, Leicester, UK.

<p> Working within the framework of the linearized Boltzmann equation for the conduction electrons the existing theoretical treatments of ultrasonic attenuation in metals are extended to include realistic descriptions of the electronic structure and electron-lattice interaction. A variational solution of the Boltzmann equation which allows the inclusion of phonon drag effects is derived. An anisotropic scattering time solution is also presented. Both of these solutions are applied to calculation of the attenuation coefficient in pure metals and dilute alloys. </p> <p> The theory of the effects of electron-electron collisions on the ultrasonic attenuation in metals is also examined. </p> / Thesis / Doctor of Philosophy (PhD)

Smart devices capable of harvesting their own energy have advantages over their wired or battery-powered alternatives including improved portability, simplified installation, and reduced maintenance and operating costs. This thesis studies energy harvesting technology through a case study of a solar-powered motorized window shade. An analytical and experimental evaluation of window attenuation found that windows reduced the ability of solar cells to produce photocurrent by 30%-70%. This still allows significant potential to power small electronics so a prototype motorized window blind was designed and assembled. The solar array was mounted to the roller blind's bottom rail and power is conveyed to the control electronics and motor in the unit’s top cylinder through wires embedded in the shade’s fabric. A simple battery system was implemented to ensure the prototype could remain powered in the absence of light. Various forms of powerflow in the prototype were evaluated. Experimental evaluation of joule heating within the conductive textile indicates that a temperature gradient that is less than 10 °C develops, meaning it is safe for use. The prototype was designed with artificial friction to prevent the blinds from slipping when not in use. An experimentally validated motor model was developed and used to determine that the system could use up to 46% less energy if the artificial friction was removed. A pseudo-empirical system model was developed to simulate the interaction between system electronics. Simulation results indicate that the system would remain consistently powered if placed behind a south-facing window that receives a consistent supply of direct sunlight and attenuates that light by less than 75%. These results also indicate that the unit would remain powered in the absence of light for 13 days. Similar methods could be used to evaluate future energy harvesting systems. / Thesis / Master of Applied Science (MASc)